Gnutella is one of several peer to peer networks, on which users can exchange files. Limewire is one of the clients that enable the users to exchange the files on the Gnutella Network. (a number of other clients includes Phex and Bearshare)
The licence question is best answered here:-
http://www.gnutellaforums.com/showth...176#post154176
which way you set it is really up to you
